Battery unit

ABSTRACT

A battery unit comprises a battery case, and a plurality of battery modules stored and held in the battery case. The battery case includes a bottom wall and a partition. The plurality of battery modules are mounted on the bottom wall. The partition is provided and erected on the bottom wall. The partition separates the battery modules adjacent in a second direction traversing a first direction. The first direction is oriented from a first end of the battery case at which an inlet is formed to a second end at which an outlet is formed. The partition extends along a plane where the battery modules face each other in the second direction along the battery modules. The partition is inclined in the extending direction.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of co-pending application Ser. No.12/411,959 filed on Mar. 26, 2009 and which is a continuation of PCT/JP2008/054806, filed Mar. 14, 2008; which claims benefit of priority to JP2007-256208, filed Sep. 28, 2007. The entire contents of each of theabove-identified applications are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a battery unit used as a power supplyfor, for example, an electric vehicle.

2. Description of the Related Art

An electric vehicle is equipped with a battery unit as a power supplyfor running. The battery unit comprises a battery module, a battery casefor storing the battery module, etc. The battery case of the batteryunit of this type includes a battery carrier for storing a battery, anda battery carrier cover for covering the battery carrier.

Lattice-shaped projections are formed in the bottom of the batterycarrier so that a plurality of batteries are held in a fitted state.Each battery module is stored in a recess defined by the projections.Each battery module stored in the battery carrier is held between thebattery carrier and the battery carrier cover. A structure of this typeis disclosed in Japanese Patent No. 2758348.

At the same time, the battery needs to be charged. There are two ways ofcharging; one of which is a quick charge for charging in a short periodof time, and the other uses, for example, a domestic power source, whichtakes more time for charging than the quick charge.

The battery module generates heat when the battery is charged. Inparticular, one great challenge for the electric vehicle is how toincrease the mileage. Therefore, the largest possible battery unit(including a plurality of battery modules) tends to be mounted. Thus, inthe case of the quick charge which completes charging in a short periodof time, the calorific value of the battery tends to be high because thebattery is charged using a high-current power supply. An increasedcalorific value of the battery leads to deterioration of the battery andis therefore not preferable.

The battery case is provided with a fan as a structure for cooling offthe battery module while the electric vehicle is running. While theelectric vehicle is running, the fan is driven to bring air into thebattery case. Each battery is cooled off by the air brought in. Astructure of this type is disclosed in Japanese Patent No. 2758348.

In order to improve the rigidity of the battery case, the lattice-shapedprojections formed in the bottom of the battery carrier may be increasedin height. However, if the projections are increased in height, the areaof each battery module covered with the projections is increased.Accordingly, the area of each battery module in contact with the airbrought into the battery case decreases. A decreased area of eachbattery module in contact with the air is not preferable in terms of thecooling of the battery module.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a batteryunit capable of maintaining sufficient rigidity of a battery case andalso efficient cooling of a battery.

A battery unit according to an aspect of the present invention comprisesa battery case having an inlet to let in a cooling gas and an outlet tolet out the gas, and a plurality of battery modules stored and held inthe battery case. The battery case includes a bottom wall and partition.The plurality of battery modules are mounted on the bottom wall. Thepartition is provided on the bottom wall. The partition separates thebattery modules adjacent in a second direction traversing a firstdirection. The first direction is oriented from a first end of thebattery case at which the inlet is formed to a second end at which theoutlet is formed. The partition extends in a plane where the batterymodules face each other in the second direction along the batterymodules. The partition is inclined in the direction of extension.

According to this structure, the rigidity of the battery case ismaintained, and at the same time, the range of the battery modulecovered with the partitions can be reduced. Thus, the area of contactbetween the battery module and the cooling gas can be increased.

Consequently, it is possible to provide a battery unit capable ofmaintaining sufficient rigidity of a battery case and also efficientcooling of a battery.

In a preferred embodiment of the present invention, the partition maybecome gradually lower toward the center of the battery case in thefirst direction.

In a further preferred embodiment of the present invention, a pluralityof partitions identical to the partition are provided. An inlet sidebattery module group and an outlet side battery module group may bearranged in the battery case, the inlet side battery module groupincluding a plurality of battery modules disposed on the side of thefirst end, the outlet side battery module group including a plurality ofbattery modules disposed on the side of the second end. A partition ofthe plurality of partitions, which separate the battery modules in theinlet side battery module group may become gradually lower toward thecenter of the battery case in the first direction. A partition of theplurality of partitions, which separate the battery modules in theoutlet side battery module group may become gradually lower toward thecenter of the battery case.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing an electric vehicle equipped with abattery unit according to one embodiment of the present invention;

FIG. 2 is a perspective view showing a frame body structure and thebattery unit of the electric vehicle shown in FIG. 1;

FIG. 3 is a side view showing the frame body structure and the batteryunit of the electric vehicle shown in FIG. 1;

FIG. 4 is a plan view showing the frame body structure and the batteryunit of the electric vehicle shown in FIG. 1;

FIG. 5 is a perspective view showing in an exploded manner the batteryunit shown in FIG. 1;

FIG. 6 is a perspective view showing in an enlarged manner a frontbattery storage shown in FIG. 5;

FIG. 7 is a perspective view showing in an enlarged manner a range of F7shown in FIG. 6;

FIG. 8 is a perspective view showing in an exploded manner a batterymodule shown in FIG. 6;

FIG. 9 is a sectional view through the front battery storage in a widthdirection when the battery modules are stored in the front batterystorage shown in FIG. 6;

FIG. 10 is a sectional view through the upper end of the front batterystorage shown in FIG. 6 in a front-back direction;

FIG. 11 is a sectional view through the battery unit shown in FIG. 1 inthe front-back direction;

FIG. 12 is a plan view showing a cover member shown in FIG. 5 from whicha fan cover and a bypass duct are removed;

FIG. 13 is a sectional view showing in an enlarged manner a range of F13shown in FIG. 11;

FIG. 14 is a perspective view showing the bypass duct and a fan unitremoved from the cover member shown in FIG. 5;

FIG. 15 is a perspective view showing in an exploded manner an exhaustduct unit shown in FIG. 14;

FIG. 16 is a sectional view showing the duct shown in FIG. 15 in theinsertion direction of an insertion portion;

FIG. 17 is a sectional view showing the rear end of the battery unitshown in FIG. 1 in the front-back direction;

FIG. 18 is a sectional view showing a fixing structure of the covermember and the fan cover shown in FIG. 17, in a part different from thepart shown in FIG. 17;

FIG. 19 is a sectional view showing the vicinity of an exhaust fanfixing portion shown in FIG. 14; and

FIG. 20 is a sectional view showing the positional relation between amotor and the battery unit shown in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

A battery unit according to one embodiment of the present invention isdescribed with FIGS. 1 to 20. FIG. 1 shows one example of an electricvehicle 10. As shown in FIG. 1, the electric vehicle 10 comprises amotor 12 for driving and a charger 13 that are arranged in the rear partof a vehicle body 11, a battery unit 14 disposed under the floor of thevehicle body 11, etc. The battery unit 14 is located ahead of the motor12. An air-conditioning heat exchanger unit 15 is disposed in the frontpart of the vehicle body 11. In addition, the motor 12 is notexclusively positioned in the rear part of the vehicle body 11. Forexample, the motor 12 may be disposed in the front part of the vehiclebody 11.

A front wheel 20 of the electric vehicle 10 is supported on the vehiclebody 11 by an unshown front suspension. A rear wheel 21 is supported onthe vehicle body 11 by an unshown rear suspension.

FIG. 2 shows the battery unit 14 separated from a frame body structure30 which forms the frame structure of the lower part of the vehicle body11. FIG. 3 is a side view showing the vehicle body 11 in which thebattery unit 14 is fixed to the frame body structure 30. FIG. 4 is aplan view showing the frame body structure 30 to which the battery unit14 is fixed.

As shown in FIGS. 2 to 4, the frame body structure 30 includes a pair ofleft and right side members 31, 32 extending in the front-back directionof the vehicle body 11, and cross members 33, 34, 35 extending in thewidth direction of the vehicle body 11. The cross members 33, 34, 35 arefixed by welding at predetermined positions of the side members 31, 32in order from the front.

FIG. 5 is a perspective view showing the battery unit 14 in an explodedmanner. As shown in FIG. 5, the battery unit 14 includes a battery case50, a plurality of battery modules 60 (some of which are shown in FIG.6) stored in the battery case 50, a monitor for detecting the state ofthe battery modules 60, and electric components (not shown) for control.

The top, bottom, front, rear, right and left of the battery unit 14correspond to the top, bottom, front, rear, right and left of thevehicle body 11 when the battery unit 14 is fixed to the frame bodystructure 30. That is, the vertical direction, front-back direction andwidth direction (lateral direction) of the battery unit 14 are the sameas the vertical direction, front-back direction and width direction ofthe vehicle body 11.

The battery case 50 includes a tray member 51 located in the lower part,and a cover member 52 located in the upper part. The planar shape of thebattery case 50 is substantially rectangular. At a front end 52 b of thecover member 52, a cooling air inlet 86 (described later in detail) isformed to let cooling air G into the battery case 50. In addition, thecooling air G is one example of a cooling gas referred to in the presentinvention. Moreover, at a rear end 52 c of the cover member 52, firstand second outlets 555, 556 (described later in detail) are formed tolet out the air inside the battery case 50.

In addition, a front end 50 a of the battery case 50 is one example of afirst end referred to in the present invention at which the cooling airinlet 86 is formed. A rear end 50 b of the battery case 50 is oneexample of a second end referred to in the present invention at whichthe first and second outlets 555, 556 are formed. Further, a front-backdirection X is one example of a first direction referred to in thepresent invention, and a width direction Y (lateral direction) is oneexample of a second direction referred to in the present invention.

A front battery storage 55 is formed in the front half of the batterycase 50. A rear battery storage 56 is formed in the rear half of thebattery case 50. Central battery storages 57, electric circuit storages58, etc. are formed between the front battery storage 55 and the rearbattery storage 56.

As shown in FIG. 3, the battery case 50 is shaped so that the centralbattery storages 57 and the electric circuit storages 58 are recessedlower than the front battery storage 55 and the rear battery storage 56.Therefore, the parts of the cover member 52 corresponding to the centralbattery storages 57 and the electric circuit storages 58 are recesseddownward.

The battery unit 14 will be described in detail later. First, astructure of fixing the battery unit 14 to the frame body structure 30is described.

As shown in FIG. 3, the battery unit 14 is disposed on the lower side ofa floor panel 70. The floor panel 70 is fixed by welding at apredetermined position of the frame body structure 30 including the sidemembers 31, 32.

As shown in FIG. 1, a front seat 71 and a rear seat 72 are arranged onthe floor panel 70. The front battery storage 55 of the battery unit 14is disposed under the front seat 71 (including a driver's seat 71 b anda the seat next to the driver 71 a). The rear battery storage 56 of thebattery unit 14 is disposed under the rear seat 72. A recess 70 a of thefloor panel 70 formed between the front battery storage 55 and the rearbattery storage 56 is located in the vicinity of a foot space for apassenger sitting on the rear seat 72.

A plurality of (e.g., four) beam members 101, 102, 103, 104 are providedon the lower side of the tray member 51. As shown in FIG. 5, the beammembers 101, 102, 103, 104 have beam bodies 111, 112, 113, 114 extendingin the width direction of the vehicle body 11, respectively.

Fastening portions 121, 122 are provided at both ends of the first beambody 111 from the front. Fastening portions 123, 124 are provided atboth ends of the second beam body 112 from the front. Fastening portions125, 126 are provided at both ends of the third beam body 113 from thefront. Fastening portions 127, 128 are provided at both ends of thefourth (rearmost) beam body 114 from the front.

The beam members 101, 102, 103, 104 are fixed to the lower surface ofthe tray member 51 by unshown bolts. The tray member 51 is provided withnuts (not shown) to which the bolts are screwed.

The beam members 101, 102, 103, 104 are made of a metal material (e.g.,steel plate) strong enough to bear the load of the battery unit 14. Morespecifically, as shown in FIGS. 3 and 4, the first beam member 101 fromthe front has a metal lower plate 141, an upper plate 142 hat-shaped insection, and the above-mentioned fastening portions 121, 122 provided atboth ends of the upper plate 142. The beam body 111 is formed by thelower plate 141 and the upper plate 142. Bolt insertion holes 143 (shownin FIG. 2 and FIG. 5) are formed vertically through the fasteningportions 121, 122.

The side members 31, 32 are provided with battery unit attachingportions 145, 146 having nut members at positions opposite to thefastening portions 121, 122. Bolts 147 (shown in FIGS. 2 and 3) areinserted into the bolt insertion holes 143 from the lower side of thefastening portions 121, 122, and the bolts 147 are screwed and fastenedto the nut members of the battery unit attaching portions 145, 146, suchthat the fastening portions 121, 122 of the first beam member 101 arefixed to the side members 31, 32.

As shown in FIGS. 3 and 4, the second beam member 102 from the front hasa metal lower plate 151, an upper plate 152 hat-shaped in section, andthe above-mentioned fastening portions 123, 124 provided at both ends ofthe upper plate 152. The beam body 112 is formed by the lower plate 151and the upper plate 152. Bolt insertion holes 153 (shown in FIG. 2 andFIG. 5) are formed vertically through the fastening portions 123, 124.

The side members 31, 32 are provided with battery unit attachingportions 155, 156 having nut members at positions opposite to thefastening portions 123, 124. Bolts 157 (shown in FIGS. 2 and 3) areinserted into the bolt insertion holes 153 from the lower side of thefastening portions 123, 124, and the bolts 157 are screwed and fastenedto the nut members of the battery unit attaching portions 155, 156, suchthat the fastening portions 122, 123 of the second beam member 102 arefixed to the side members 31, 32.

The third beam member 103 from the front has a metal lower plate 161, anupper plate 162 hat-shaped in section, and the above-mentioned fasteningportions 125, 126 provided at both ends of the upper plate 162. The beambody 113 is formed by the lower plate 161 and the upper plate 162. Boltinsertion holes 163 (shown in FIG. 2 and FIG. 5) are formed verticallythrough the fastening portions 125, 126.

As shown in FIGS. 3 and 4, metal load transfer members 170, 171 arefixed to the side members 31, 32 by bolts 172, respectively. The loadtransfer members 170, 171 are provided at opposite positions above thefastening portions 125, 126 of the third beam member 103 from the front.One load transfer member 170 is welded to one suspension arm supportbracket 40 of the rear suspension which supports the rear wheel 21. Theother load transfer member 171 is welded to the other suspension armsupport bracket (not shown).

In addition, the load transfer member 170 is shown in FIG. 3. The loadtransfer member 171 may be similar in structure to the load transfermember 170. The one suspension arm support bracket 40 is shown in FIG.3. The other suspension arm support bracket (not shown) may be similarto the one suspension arm support bracket 40.

That is, the load transfer members 170, 171 are linked to the sidemembers 31, 32 and the suspension arm support brackets 40, 41. The loadtransfer members 170, 171 form part of the frame body structure 30. Theload transfer members 170, 171 are provided with battery unit attachingportions 175, 176 having nut members.

Bolts 177 are inserted into the bolt insertion holes 163 from the lowerside of the fastening portions 125, 126, and the bolts 177 are screwedand fastened to the nut members of the battery unit attaching portions175, 176, such that the fastening portions 125, 126 of the third beammember 103 are fixed to the side members 31, 32 via the load transfermembers 170, 171.

The fourth beam member 104 from the front also has a metal lower plate191, an upper plate 192 hat-shaped in section, and the above-mentionedfastening portions 127, 128 provided at both ends of the upper plate192. The beam body 114 is formed by the lower plate 191 and the upperplate 192. Bolt insertion holes 193 (shown in FIG. 2 and FIG. 5) areformed vertically through the fastening portions 127, 128.

The side members 31, 32 are provided with extension brackets 194, 195 atpositions opposite to the fastening portions 127, 128. The extensionbrackets 194, 195 extend under kick-up portions 31 b, 32 b of the sidemembers 31, 32. The extension brackets 194, 195 form part of the framebody structure 30. The extension brackets 194, 195 are provided withbattery unit attaching portions 196, 197 having nut members.

Bolts 198 (shown in FIGS. 2 and 3) are inserted into the bolt insertionholes 193 from the lower side of the fastening portions 127, 128, andthe bolts 198 are screwed and fastened to the nut members of the batteryunit attaching portions 196, 197 of the extension brackets 194, 195,such that the fastening portions 127, 128 of the fourth beam member 104are fixed to the side members 31, 32 via the extension brackets 194,195.

As shown in FIG. 3, the lower surfaces of the beam members 101, 102,103, 104 are located on the same horizontally extending plane L alongthe flat lower surface of the tray member 51. The first and second beammembers 101, 102 are directly fixed to the battery unit attachingportions 145, 146, 155, 156 provided at horizontal portions 31 a, 32 aof the side members 31, 32.

The third beam member 103 and the fourth beam member 104 are fixed tothe battery unit attaching portions 175, 176, 196, 197 provided at thekick-up portions 31 b, 32 b of the side members 31, 32.

The third and fourth beam members 103, 104 are located at offsetpositions under the kick-up portions 31 b, 32 b. Thus, the third beammember 103 is fixed to the battery unit attaching portions 175, 176 viathe load transfer members 170, 171 having a thickness in the verticaldirection. The fourth beam member 104 is fixed to the battery unitattaching portions 196, 197 by the extension brackets 194, 195 extendingunder the kick-up portions 31 b, 32 b.

In the electric vehicle 10 in the present embodiment, the beam members101, 102, 103, 104 are provided across the left and right side members31, 32, and the side members 31, 32 are linked together by the beammembers 101, 102, 103, 104. Thus, the beam members 101, 102, 103, 104 ofthe battery unit 14 function as rigid members corresponding to the crossmembers.

Next, the battery unit 14 is specifically described.

As described above, the battery unit 14 includes the battery case 50,the battery modules 60 (some of which are shown in FIG. 6), the monitorfor detecting the state of the battery modules 60, the electriccomponents (not shown) for control, a plurality of ribs 523, a bypassduct cover 531, a fan unit 550 and a battery protector 620.

The tray member 51 is a molded article in which a reinforcing metalplate is inserted into an integrally molded synthetic resin. The traymember 51 is molded into a box shape with an open upper side. Thesynthetic resin, which is the material of the tray member 51, isreinforced by, for example, fiber. The planar shape of the tray member51 is substantially rectangular.

As shown in FIG. 5, a cover attachment surface 80 is formed on theperipheral edge of the upper surface of the tray member 51. The coverattachment surface 80 is continuous over the whole circumference of thetray member 51. A waterproof seal member (not shown) is provided on thecover attachment surface 80.

The cover member 52 is made of an integrally molded article of asynthetic resin reinforced by fiber. The cover member 52 covers theopening at the upper end of the tray member 51. The cover member 52 isformed into a box shape opening on the side of the tray member 51. Theplanar shape of the cover member 52 is substantially rectangular.

A flange 95 is formed on the peripheral edge of the end of the openingin the cover member 52. The flange 95 is continuous over the wholecircumference of the cover member 52. The flange 95 of the cover member52 is mounted on the cover attachment surface 80 of the tray member 51,and the flange 95 and the cover attachment surface 80 are watertightlyfixed together by bolts 96 or nuts 97 via the seal member interposedbetween the tray member 51 and the cover member 52.

As shown in FIG. 5, the front battery storage 55, the rear batterystorage 56, the central battery storages 57 and the electric circuitstorages 58 are formed in the battery case 50.

A front battery module group 501 is disposed in the front batterystorage 55. The front battery module group 501 is composed of aplurality of battery modules 60. A plurality of front battery storagechambers 502 are formed in the front battery storage 55. Each of thefront battery storage chambers 502 is formed by a plurality of frontlongitudinal partitions 503 and a front widthwise partition 504.

The front longitudinal partitions 503 are formed on a bottom wall 505,and arranged separately from each other in the width direction so thatthese partitions are erected from the bottom wall 505 of the tray member51. Moreover, each of the front longitudinal partitions 503 extendsrearward with its one end coupled to a front end 506 a of a peripheralwall 506 of the tray member 51. In the present embodiment, for example,four front longitudinal partitions 503 are used. The front longitudinalpartitions 503 are one example of partitions referred to in the presentinvention.

The front widthwise partition 504 is provided on the bottom wall 505 inthe vicinity of the rear ends of the front longitudinal partitions 503.The front widthwise partition 504 is erected from the bottom wall 505and extends from one end to the other in the vehicle width direction ofthe tray member 51 so that both ends of the front widthwise partition504 are coupled to the peripheral wall 506. The rear ends of the frontlongitudinal partitions 503 are coupled to the front widthwise partition504.

As described above, spaces defined between the peripheral wall 506 ofthe tray member 51, the front longitudinal partitions 503 and the frontwidthwise partition 504 serve as the front battery storage chambers 502.In the present embodiment, five front battery storage chambers 502 areformed side by side in the width direction. In addition, the number ofthe front battery storage chambers 502 is not limited to five.

FIG. 6 shows the front battery storage 55 in an enlarged manner. Asshown in FIG. 6, the battery modules 60 are stored in each of the frontbattery storage chambers 502. In the present embodiment, the frontbattery storage chamber 502 is formed to be long in the front-backdirection, and stores two battery modules 60 in the front-backdirection. Moreover, the breadth of the front battery storage chamber502 in the width direction is sized so that one battery module 60 isstored. The front longitudinal partitions 503 are inclined to becomegradually lower rearward.

The position of the upper surface of the front widthwise partition 504is set to be flush with, for example, the cover attachment surface 80 ofthe tray member 51. Thus, the upper surfaces of the rear ends (partscoupled to the front widthwise partition 504) of the front longitudinalpartitions 503 are lower than the upper surface of the front widthwisepartition 504.

FIG. 7 is a perspective view showing in an enlarged manner a range of F7shown in FIG. 6. FIG. 7 shows a part where the front longitudinalpartition 503 and the front widthwise partition 504 are coupledtogether. As shown in FIG. 7, the part of the front widthwise partition504 coupled to the front longitudinal partition 503 is cut to theposition of the upper surface of the front longitudinal partition 503.This cut 504 a penetrates in the front-back direction.

As shown in FIG. 5, a rear battery module group 507 (part of which isshown) is stored in the rear battery storage 56. The rear battery modulegroup 507 is composed of the plurality of battery modules 60. Aplurality of rear battery storage chambers 508 are formed in the rearbattery storage 56. Each of the rear battery storage chambers 508 isformed by a plurality of rear longitudinal partitions 509 and a rearwidthwise partition 510.

The rear longitudinal partitions 509 are formed on the bottom wall 505,and arranged separately from each other in the width direction anderected. Moreover, each of the rear longitudinal partitions 509 extendsforward with its one end coupled to a rear end 506 b of the peripheralwall 506 of the tray member 51. In the present embodiment, for example,four rear longitudinal partitions 509 are used. The rear longitudinalpartitions 509 are one example of partitions referred to in the presentinvention.

The rear widthwise partition 510 is provided on the bottom wall 505 inthe vicinity of the front ends of the rear longitudinal partitions 509.The rear widthwise partition 510 is erected from the bottom wall 505 andextends from one end to the other in the width direction of the traymember 51 so that both ends of the rear widthwise partition 510 arecoupled to the peripheral wall 506. The front ends of the rearlongitudinal partitions 509 are coupled to the rear widthwise partition510.

As described above, spaces defined between the peripheral wall 506 ofthe tray member 51, the rear longitudinal partitions 509 and the rearwidthwise partition 510 serve as the rear battery storage chambers 508.In the present embodiment, five rear battery storage chambers 508 areformed side by side in the width direction. Similarly to the frontbattery storage chamber 502, the rear battery storage chamber 508 isformed so that two battery modules 60 arranged in the front-backdirection are stored therein. In addition, the number of the rearbattery storage chambers 508 is not limited to five. The rearlongitudinal partitions 509 are inclined to become gradually lowerforward.

The position of the upper surface of the rear widthwise partition 510 isset to be flush with, for example, the cover attachment surface 80 ofthe tray member 51. Thus, the upper surfaces of the front ends (partscoupled to the rear widthwise partition 510) of the rear longitudinalpartitions 509 are lower than the upper surface of the rear widthwisepartition 510. Thus, similarly to the front widthwise partition 504, thepart of the rear widthwise partition 510 coupled to the rearlongitudinal partition 509 is cut to the position of the upper surfaceof the rear longitudinal partition 509. This cut 510 a penetrates in thefront-back direction.

The front and rear longitudinal partitions 503, 509 and the front andrear widthwise partitions 504, 510 also function as reinforcing walls ofthe tray member 51. Thus, the heights of the front and rear longitudinalpartitions 503, 509 and the front and rear widthwise partitions 504, 510are set so that the rigidity necessary for the tray member 51 may beensured. However, the front and rear longitudinal partitions 503, 509are inclined in the front-back direction, so that the areas of the sidesurfaces of the battery modules 60 covered with the front and rearlongitudinal partitions 503, 509 are reduced.

As shown in FIG. 5, the central battery storages 57 and the electriccircuit storages 58 are arranged between the front and rear widthwisepartitions 504, 510. One electric circuit storage 58 is disposed at eachof both right and left front ends. The central battery storages 57 aredisposed behind the electric circuit storages 58, and one centralbattery storage 57 is disposed at each of both right and left ends.

A plurality of partitions extending in the front-back direction andwidth direction are formed to partition the central battery storages 57and the electric circuit storages 58. Among these partitions, centrallongitudinal partitions 511 extending in the front-back direction areformed to be lower than the front and rear widthwise partitions 504,510.

Furthermore, among the plurality of central longitudinal partitions 511,the central longitudinal partitions located at the positions where thecuts 504 a of the front widthwise partitions 504 are coupled to the cuts510 a of the rear widthwise partitions 510 are formed to be flush withthe lower ends of the cuts 504 a, 510 a. That is, as shown in FIG. 7,the front longitudinal partition 503 and the central longitudinalpartition 511 are flush with and continuous to each other. Similarly,the rear longitudinal partition 509 and the central longitudinalpartition 511 are flush with and continuous to each other. The cuts 504a, 510 a are therefore not closed by the central longitudinal partitions511.

In addition, a plurality of battery storage chambers are not formed inthe central battery storage 57, and a plurality of unshown batterymodules 60 are stored in the central battery storage 57. The electriccircuit storages 58 store the monitor for detecting the state of thebattery modules 60 and the electric components for control.

FIG. 8 shows one battery module 60. As shown in FIG. 8, the batterymodule 60 includes four battery cells 512 composed of lithium ionbatteries, and a cell holder 513 for holding the four battery cells 512.In addition, one battery cell 512 is shown in an enlarged manner withina zone indicated by a two-dot chain line in FIG. 8. The battery cells512 are held by the cell holder 513 so that these battery cells areelectrically connected to each other in series. The battery modules 60are electrically connected to each other in series. In addition, thetop, bottom, front, rear, right and left of the battery module 60correspond to the top, bottom, front, rear, right and left of thebattery unit 14 when this battery module 60 is disposed in the batterycase 50.

The cell holder 513 has a holder body 514 and a lid 515. The holder body514 is substantially in the shape of a rectangular parallelepiped. Oneof the widthwise side walls of the holder body 514 (side surfaceopposite to the peripheral wall 506 of the tray member 51 or the frontand rear longitudinal partitions 503, 509) is open. Moreover, the lowerend face of the holder body 514 is open.

The lid 515 removably covers the opening in the side surface of theholder body 514. The lid 515 is removed when battery cells 512 arestored in or taken out of the cell holder 513. A plurality of coolingholes 516 are formed in the wall surfaces of the holder body 514 and thelid 515 for cooling the cells.

Legs 517 to be in contact with the bottom wall 505 of the tray member 51are formed at the lower end of the holder body 514 and the lower end ofthe lid 515. The legs 517 are formed, for example, in all the regions ofthe lower ends of the holder body 514 and the lid 515 in the front-backdirection.

FIG. 9 is a sectional view of the vicinity of the tray member 51 in thewidth direction. FIG. 9 shows a section through the front batterystorage 55 in the width direction when the battery modules 60 is storedin the front battery storage chamber 502.

As shown in FIG. 9, the legs 517 project inward in the battery module 60in the width direction. Therefore, the positions of the legs 517 to bein contact with the bottom wall 505 are within a range A in which thebottom wall 505 faces the battery modules 60. Moreover, the legs 517 areshaped to extend and project downward, so that a space S1 is definedbetween the bottom wall 505 and each of the battery cells 512.

Here, the width of the front battery storage chamber 502 and a border518 between the bottom wall 505 and the front longitudinal partition 503are specifically described.

The width of the front battery storage chamber 502 is sized so that thetolerance of the shape of the battery module 60 is added to the width ofthe battery module 60. Thus, a slight space S2 may be present betweenthe front longitudinal partition 503 and the battery module 60 as shownin FIG. 9. The border 518 between the bottom wall 505 and the frontlongitudinal partition 503 is continuous in the shape of a smooth arc.Therefore, when the tray member 51 is cast in a mold orinjection-molded, the fluidity of a resin in a part corresponding to theborder 518 improves in a mold (not shown) for molding the tray member51.

The border 518 is shown in an enlarged manner within a zone indicated bya two-dot chain line in FIG. 9. As described above, the legs 517 areshaped to project inward in the width direction, so that the legs 517avoid the borders 518 and thus do not interfere with the borders 518even when, for example, the battery module 60 is fitted into the frontbattery storage chamber 502 in the width direction (when the batterymodule 60 is in contact with the front longitudinal partition 502 asindicated by a two-dot chain line in FIG. 9).

It is preferable that the legs 517 project inward in the width directionto such a degree that the legs 517 do not interfere with the borders 518and to such a degree that the legs 517 are not located too far from thefront longitudinal partitions 503 in the width direction (lateraldirection). The legs 517 are not located far from the front longitudinalpartitions 503 in the width direction such that the bottom wall 505 isinhibited from being deformed by the weight of the battery modules 60.

While the border 518 between the bottom wall 505 and the frontlongitudinal partition 503 and the width of the front battery storagechamber 502 have been described, the border between the bottom wall 505and the rear longitudinal partition 509 is also smoothed. The width ofthe rear battery storage chamber 508 is also similar to the frontbattery storage chamber 502. Moreover, the border between the bottomwall 505 and the peripheral wall 506 of the tray member 51 (a borderwith a part in the front-back direction and a border with a part alongthe vehicle width direction) is also smoothed.

FIG. 10 is a section through the upper end of the front battery storage55 in the front-back direction, and shows the front end of the covermember 52 and the front end of the battery module 60 located on thefront side of the front battery storage 55.

As shown in FIGS. 8 and 10, cuts 520 are formed in upper corners 519 atthe front and rear ends of the holder body 514 of the battery module 60.The cooling holes 516 are disposed in the corners 519 to form the cuts520.

As shown in FIG. 10, a front end 521 a of a peripheral wall 521 of thecover member 52 extends rearward in the upward direction and istherefore inclined. Thus, even if the corner 519 of the cell holder 513comes into contact with the inner surface of the front end 521 a of theperipheral wall 521 of the cover member 52, air flows through the cut520 formed in the corner 519 as indicated by arrows in FIG. 10, so thatthe flow of the cooling air in the battery case 50 is not blocked by thebattery module 60.

Although the cuts 520 are formed in the corners 519 at the front andrear ends of the cell holder 513 in the exemplar described in thepresent embodiment, similar cuts may be formed in upper corners of thecell holder 513 in the width direction (lateral direction). In thiscase, even when the inner surfaces of the right and left ends of theperipheral wall 521 of the cover member 52 come into contact with thewidthwise corners of the cell holder 513, air flows through the cutsformed in the widthwise corners, so that the flow of the cooling air inthe battery case 50 is not blocked.

FIG. 11 is a sectional view through the battery unit 14 in thefront-back direction, and shows the flow of the cooling air let in fromthe cooling air inlet 86.

As shown in FIG. 1, the cooling air inlet 86 is formed in the part ofthe cover member 52 located under the seat next to the driver 71 a. Thecooling air inlet 86 is connected by a cooling air duct 522 to the heatexchanger unit 15 disposed in the front part of the vehicle body 11.That is, the cooling air inlet 86 is disposed at the front left end ofthe cover member 52.

Incidentally, there are two ways of charging the battery unit 14; forexample, one of which is a quick charge for charging in a short periodof time, and the other uses, for example, a domestic power source totake a longer time for charging than the quick charge. In the case ofthe quick charge, the battery module 60 generates heat. Thus, thebattery unit 14 is cooled off when quick-charged. During the quickcharge, the cooling air is blown from the heat exchanger unit 15 throughthe cooling air duct 522. The cooling air duct 522 is positioned at thefoot of the seat next to the driver 71 a.

As shown in FIG. 11, the ribs 523 are fixed to a lower surface 52 a ofthe cover member 52. Specifically, on the lower surface 52 a of thecover member 52, two ribs 523 are fixed separately in the front-backdirection in a range facing the front battery storage 55, and two ribs523 are fixed separately in the front-back direction in a range facingthe rear battery storage 56.

FIG. 12 is a plan view showing the cover member 52. In FIG. 12, thebypass duct cover 531, the fan unit 550 and the battery protector 620that will be described later are removed in FIG. 12. The ribs 523 areindicated by dashed lines in FIG. 12. The forefront rib 523 extends inthe width direction from a position which does not overlap the coolingair inlet 86 in the front-back direction so that the flow of the coolingair from the cooling air inlet 86 may not be prevented. The other threeribs 523 extend from one end of the cover member 52 to the other in thewidth direction.

As shown in FIG. 11, the ribs 523 project downward from the lowersurface 52 a of the cover member 52 and are in contact with the uppersurfaces of the battery modules 60. FIG. 13 is a sectional view showingin an enlarged manner a range of F13 shown in FIG. 11. FIG. 13 shows apart where the rib 523 is in contact with the battery module 60.

As shown in FIG. 13, the rib 523 is T-shaped in section and formed of adeformable elastic body. By way of example, rubber is used as thematerial of the rib 523. The rib 523 is sized so that its tip 523 aslightly deforms as shown to ensure contact with the upper surface ofthe battery module 60 when the cover member 52 is fixed to the traymember 51. This ensures that the rib 523 comes into contact with theupper surface of the battery module 60. As indicated by arrows in FIG.11, the ribs 523 function to guide the cooling air flowing in the upperpart of the battery case 50 to the lower part.

In addition, the number of the ribs 523 is not limited to four.Moreover, the section of the rib 523 is not exclusively T-shaped and maybe, for example, rectangular. The ribs 523 are members separate from thecover member 52. Therefore, the shape of the ribs 523 is easily adjustedto the size of the battery modules 60. Although the ribs 523 are fixedto the cover member 52, the ribs 523 may be fixed to the upper surfacesof the battery modules 60 (the upper surfaces of the housings 514) andcome into contact with the cover member 52.

The bypass duct cover 531 functions to guide the cooling air flowing infrom the cooling air inlet 86 to the downstream of the front batterystorage 55 in such a manner as to bypass the front battery storage 55.As shown in FIGS. 2, 4 and 5, the bypass duct cover 531 is attached tothe upper surface of the cover member 52. FIG. 14 shows the bypass ductcover 531 removed from the cover member 52. As shown in FIG. 14, abypass exit opening 534 is formed in the upper wall of the cover member52 opposite to the cooling air inlet 86, that is, on the side of thedriver's seat 71 b.

The bypass exit opening 534 pierces the cover member 52. Moreover, asshown in FIG. 12, a bypass entrance opening 535 is formed in the part ofthe upper wall of the cover member 52 located behind the front batterystorage 55. The bypass entrance opening 535 is located in the center ofthe width direction of the cover member 52.

The bypass duct cover 531 is fixed to the upper surface of the covermember 52 to cover the bypass exit opening 534 and the bypass entranceopening 535. As shown in FIGS. 10 and 11, the section of the bypass ductcover 531 is concave so that an opening is formed on the side of thecover member 52. A flow path is defined between the bypass duct cover531 and the upper surface of the cover member 52 so that the cooling airwhich has exited from the bypass exit opening 534 can flow to the bypassentrance opening 535.

In addition, as shown in FIG. 12, the forefront rib 523 is located rightbehind the bypass exit opening 534. Thus, part of the cooling air let infrom the cooling air inlet 86 is guided to the bypass exit opening 534by the forefront rib 523.

As shown in FIG. 14, a circumferentially extending flange 536 is formedon the peripheral edge of the bypass duct cover 531. The flange 536comes into contact with the upper surface of the cover member 52. Thepart of the flange 536 located substantially in the center of thefront-back direction is fastened to the cover member 52 by a total offour bolts 537 and a total of four nuts 538; two bolts and two nuts oneach of right and left sides. In this case, the bolts 537 are insertedfrom the side of the cover member 52.

Metal plates 539 are interposed between the cover member 52 and thebolts 537. Similarly, metal plates 540 are interposed between the flange536 of the bypass duct cover 531 and the nuts 538. Thus, the resin covermember 52 and the flange 536 are fastened to each other by the bolts 537and the nuts 538 with the pairs of metal plates 539, 540 interposed inbetween, so that the cover member 52 and the flange 536 are inhibitedfrom being deformed due to the fastening force by the bolts 537 and thenuts 538.

The flange 536 is fixed to the cover member 52 by welding using bosses541 except for the parts fastened by the bolts 537 and the nuts 538.This is specifically described. The front end of the bypass duct cover531 is shown in an enlarged manner within a zone indicated by a two-dotchain line in FIG. 14.

As shown in FIG. 14, the downwardly projecting bosses 541 are formed inthe flange 536 except for the middle parts in the front-back direction(except for the parts fastened by the bolts 537 and the nuts 538). Thebosses 541 are thinner than the bolts 537. Insertion holes 542 for theinsertion of the bosses 541 are formed in the parts of the cover member52 facing the bosses 541 of the flange 536. The bosses 541 are formed inthe whole region of the flange 536 (the whole region except for theparts fastened by the bolts 537 and the nuts 538).

FIG. 10 shows how the front end of the flange 536 of the bypass ductcover 531 is linked to the front end of the cover member 52 by weldingusing the bosses 541. As shown in FIG. 10, the bosses 541 insertedthrough the insertion holes 542 are melted to weld the flange 536 andthe cover member 52 together. Other parts of the flange 536 are linkedto the cover member 52 in a manner similar to the linkage shown in FIG.10.

The front end of the flange 536 is fixed to the cover member 52 bywelding using the bosses 541, so that the width of the front end of theflange 536 has only to have a size necessary to form the bosses 541. Asdescribed above, the bosses 541 are thinner than the bolts 537.Therefore, the width of the front end of the flange 536 in thefront-back direction can be reduced.

As a result, the longitudinal width of an edge 543 from the front end ofthe cover member 52 to the bypass exit opening 534 can be reduced.Therefore, when the cooling air flows into the bypass duct cover 531through the bypass exit opening 534, pressure loss due to the blowing ofthe cooling air against the edge 543 is inhibited, and the flow path isinhibited from being formed into a step shape by the edge 543.

In addition, the rear end of the flange 536 is also fixed to the covermember 52 by welding using the bosses 541, so that similar effects canalso be obtained when the cooling air flows into the battery case 50from the bypass duct cover 531 through the bypass entrance opening 535.

Thus, the bypass exit opening 534 is disposed ahead of the front batterystorage 55, and the bypass entrance opening 535 is disposed behind thefront battery storage 55, so that part of the cooling air let in fromthe cooling air inlet 86 bypasses the front battery storage 55 and flowsto the downstream of the front battery storage 55.

As shown in FIG. 14, a tunnel 532 is formed behind the bypass entranceopening 535 in the cover member 52. The tunnel 532 is disposed betweenthe electric circuit storages 58 in the cover member 52. The tunnel 532has an upwardly bulging sectional shape.

As described above, the cover member 52 is recessed in the vicinity ofthe electric circuit storages 58 as compared with the parts of the frontbattery storage 55 and the rear battery storage 56. Therefore, there isno space for the cooling air to flow in the vicinity of the electriccircuit storages 58. The cooling air flows through the tunnel 532without flowing in the vicinity of the electric circuit storages 58. Theintention in doing this is to inhibit water contained in the cooling airfrom being blown against the electric components in the electric circuitstorages 58 due to the blowing of the cooling air against the electriccircuit storages 58.

As shown in FIG. 4, a cross member 34 of the frame body structure 30 isdisposed above the tunnel 532. Thus, as shown in FIG. 2, a concaveportion 34 a for receiving the tunnel 532 is formed in the part of thecross member 34 facing the tunnel 532 in order to avoid any interferencewith the tunnel 532. In addition, a cross member in which a concaveportion is formed to pass, for example, a propeller shaft may be used asthe cross member 34.

The tunnel 532 extends to the vicinity of the central battery storages57. A two-way flow path 533 divided into right and left sides is formedbehind the tunnel 532 in the cover member 52. The left flow path of thetwo-way flow path 533 is a first flow path 533 a. The right flow path isa second flow path 533 b. The first and second flow paths 533 a, 533 bare in communication with the tunnel 532.

Parts of the first and second flow paths 533 a, 533 b are located abovethe left and right central battery storages 57. Thus, the cooling airwhich has passed through the tunnel 532 cools off the battery modules 60stored in the central battery storages 57 when passing through the firstand second flow paths 533 a, 533 b. The first and second flow paths 533a, 533 b are in communication with the rear battery storage 56 in thebattery case 50.

The fan unit 550 is disposed on the upper surface of the part of thecover member 52 corresponding to the rear battery storage 56. FIG. 14 isa perspective view showing the fan unit 550 in an exploded state. Asshown in FIG. 14, the fan unit 550 includes an exhaust fan 551, a fancover 552 and an exhaust duct unit 553.

FIG. 12 is a plan view showing the exhaust fan 551 attached to the covermember 52. The exhaust duct unit 553 is attached to the exhaust fan 551in FIG. 12. As shown in FIG. 12, the exhaust fan 551 is disposed closerto one end of the cover member 52 than the center of the cover member 52in the width direction (lateral direction), in this embodiment, disposedcloser to right end of the cover member 52. That is, the exhaust fan 551is disposed at the end opposite to the cooling air inlet 86 in the widthdirection of the vehicle body 11.

Although not shown, a cable for a parking brake and a pipe for a coolingliquid of the motor 12 (a pipe laid between the motor 12 and a radiatorlocated in the front part of the vehicle) pass through the center of thevehicle body 11 in the vehicle width direction. Moreover, the exhaustduct unit 553 described later is attached to the exhaust fan 551.

Thus, in order to avoid any interference with the cable for the parkingbrake and the cooling liquid pipe and to allow for the exchange of theexhaust duct unit 553, the exhaust fan 551 is disposed closer to oneside in the vehicle width direction as described above. As the exhaustfan 551 is closer to one side in the vehicle width direction, the handof an operator easily reaches a filter 561 of the exhaust duct unit 553when the filter 561 is exchanged. Therefore, there is no need to removethe battery unit 14, so that the efficiency of the exchange operationimproves.

The exhaust fan 551 is, for example, a sirocco fan. As indicated byarrows in FIG. 12, the exhaust fan 551 sucks the cooling air from thecenter. As shown in FIG. 14, a fan exhaust opening 558 of the exhaustfan 551 is oriented forward, and therefore discharges the cooling airforward. The exhaust duct unit 553 is attached to the fan exhaustopening 558.

As shown in FIG. 12, the first outlet 555 and the second outlet 556 areformed in the cover member 52. The first outlet 555 is disposed at theright end of the rear end of the cover member 52. The second outlet 556is disposed at the left end of the rear end of the cover member 52. Thefirst and second outlets 555, 556 pierce the cover member 52 so that thecooling air in the battery case 50 is discharged to the outside throughthe first and second outlets 555, 556.

As shown in FIG. 14, the fan cover 552 is attached to the cover member52 to cover the exhaust fan 551 and the first and second outlets 555,556 from above. The fan cover 552 is in the shape of a box having anopening on the lower side (on the side of the cover member 52), andstores the exhaust fan 551 therein. The fan cover 552 also functions asa flow path for guiding the cooling air discharged from the first andsecond outlets 555, 556 to the exhaust fan 551.

A circumferentially outwardly extending flange 557 is formed on theperipheral edge of the fan cover 552. The flange 557 is liquid-tightlyand airtightly fixed to the upper surface of the cover member 52.Moreover, a fan cover outlet 559 is formed in the part of the fan cover552 facing the fan exhaust opening 558 of the exhaust fan 551. The fanexhaust opening 558 and the fan cover outlet 559 are open forward.

A fixing structure of the fan cover 552 and the cover member 52 and afixing structure of the exhaust fan 551 and the cover member 52 will bedescribed later in detail.

The fan cover 552 is liquid-tightly and airtightly attached to the uppersurface of the cover member 52, so that the exhaust fan 551 sucks outthe cooling air G in the battery case 50 through the first and secondoutlets 555, 556. In this case, the first outlet 555 is disposed in thevicinity of the exhaust fan 551, and the second outlet 556 is disposedon the opposite side of the exhaust fan 551 in the width direction.

Thus, the first outlet 555 is formed to be smaller than the secondoutlet 556. The second outlet 556 is formed to be long in the widthdirection. The reason for this is that the suction force acting on thefirst outlet 555 is greater than the suction force acting on the secondoutlet 556 due to the difference in distance from the first and secondoutlets 555, 556 to the exhaust fan 551.

The first outlet 555 is smaller because the suction force acting on thefirst outlet 555 is greater. The second outlet 556 is larger because thesuction force acting on the second outlet 556 is smaller. The sizes ofthe first and second outlets 555, 556 are set so that the amounts of thecooling air sucked out may be substantially equal.

As a result, the amounts of the cooling air toward the first and secondoutlets 555, 556 (the amounts of the cooling air toward both rear endsof the rear battery storage 56) are equal in the rear battery storage56, so that the battery modules 60 in the rear battery storage 56 areequally cooled off.

Furthermore, the cooling air inlet 86 is disposed opposite to the firstoutlet 555 in the width direction, so that the efficiency of cooling offthe battery modules 60 in the rear battery storage 56 improves. Thistakes advantage of the fact that the first outlet 555 is smaller and theflow of the cooling air toward the first outlet 555 is therefore fasterthan the flow of the cooling air toward the second outlet 556. Thediagonal flow of the cooling air in the battery case 50 is thus fast sothat the cooling air efficiently flows through the entire battery case50. In addition, the cooling air inlet 86 is not exclusively disposed atthe end (in the present embodiment, front left end) opposite to thefirst outlet 555. The effects described above can be obtained as long asthe cooling air inlet 86 is disposed in a range opposite to the end atwhich the first outlet 555 is disposed across the center of the widthdirection of the battery case 50 (a range from the above-mentionedcenter to the end opposite to the end at which the first outlet 555 isdisposed).

FIG. 15 is a perspective view showing the exhaust duct unit 553 in anexploded manner. As shown in FIG. 15, the exhaust duct unit 553 includesan exhaust duct 560, the filter 561, a filter fixing member 562 and aseal member 562 a.

The side surface of the exhaust duct 560 is substantially L-shaped. Oneend 563 of the exhaust duct 560 is, for example, cylindrical, and isfitted into the fan exhaust opening 558 of the exhaust fan 551 throughthe fan cover outlet 559. FIG. 16 is a sectional view showing the oneend 563 fitted in the fan exhaust opening 558 in the insertion directionof the one end 563. As shown in FIG. 16, the one end 563 is fitted inthe fan exhaust opening 558 in a direction traversing the verticaldirection. The tip of the one end 563 is open, so that the cooling airdischarged from the exhaust fan 551 is guided into the exhaust duct unit553.

A circumferentially extending flange 564 is formed at the one end 563 ofthe exhaust duct 560. When the one end 563 is fitted in the fan exhaustopening 558 through the fan cover outlet 559, the flange 564 is incontact with the periphery of the fan cover outlet 559 on the outersurface of the fan cover 552.

The outer surface of the periphery of the fan cover outlet 559 of thefan cover 552 has a shape following the flange 564, so that the flange564 may come into stable surface contact. For example, the outer surfaceof the periphery of the fan cover outlet 559 is formed flat.

As shown in FIG. 14, outwardly projecting bolts 565 are provided in theparts of the fan cover 552 overlapping the flange 564. The bolts 565 areparallel with the direction (direction traversing the verticaldirection) of the insertion of the one end 563 into the fan exhaustopening 558. Bolt insertion holes 566 for the insertion of the bolts 565are formed in the parts of the flange 564 facing the bolts 565. Thebolts 565 which have passed through the bolt insertion holes 566 passthrough washers 567 and are screwed to nuts 568, such that the exhaustduct 560 is fixed to the fan cover 552. Collars 569 into which the bolts565 are inserted are inserted into the bolt insertion holes 566.

Although not shown, the flange 564 and the fan cover 552 areliquid-tightly sealed, thereby preventing a liquid such as water fromentering the fan cover 552 from the junction between the exhaust duct560 and the fan cover 552. Moreover, the direction in which the exhaustduct 560 and the fan cover 552 are linked together (direction in whichthe one end 563 is inserted) traverses the vertical direction, so that aliquid such as water does not easily enter from the junction between theexhaust duct 560 and the fan cover 552.

As described above, the exhaust duct 560 is substantially L-shaped, andthe other end 570 is therefore open downward. In addition, the exhaustduct 560 is disposed on the upper surface of the cover member 52 so thatthe exhaust duct 560 has a predetermined height from the ground. Thus,even when the electric vehicle 10 runs through a puddle, a duct opening571 at the other end 570 of the exhaust duct 560 is not easily splashedwith water.

Furthermore, the duct opening 571 of the exhaust duct 560 is orientedforward. Thus, even when the rear wheel 21 raises water, the raisedwater does not easily reach the duct opening 571. Moreover, the flowpath in the exhaust duct 560 is L-shaped, so that water does not easilyenter the fan cover 552. Thus, the entry of water into the fan cover 552through the duct opening 571 is inhibited.

As shown in FIG. 15, the filter 561 covers the whole duct opening 571 ofthe exhaust duct 560 from beneath. The filter fixing member 562 isremovably attached to the other end 570 from beneath across the filter561. The filter fixing member 562 has a lower wall 572 overlapping thelower surface of the filter 561. A plurality of through-holes are formedin the lower wall 572, and the flow of the cooling air discharged fromthe duct opening 571 is therefore not blocked.

As described above, since the battery modules 60 are, by way of example,cooled off when charged, the outside (outer surface) of the filter 561gathers, for example, dust during normal driving of the electric vehicle10. Then, during the cooling of the battery modules 60, the cooling airis discharged from the inside (surface facing the inside of the exhaustduct 560) of the filter 561 to the outside. At the same time, the dustand the like gathered on the outside of the filter 561 are removed bythe cooling air, so that the filter 561 is inhibited from being cloggedby the dust and the like.

Furthermore, as described above, the duct opening 571 is not easilysplashed with water owing to the arrangement and shape of the exhaustduct 560. Therefore, the filter 561 has only to function to prevent theentry of dust and the like without considering the entry of a liquidsuch as water. Thus, the cooling air discharged to the outside moreeasily passes through the filter 561, resulting in reduced pressure lossof flow during passage through the filter 561. This improves thecirculation of the cooling air inside the battery case 50, so that thebattery modules 60 are efficiently cooled off.

A pair of claw portions 573 are formed in the filter fixing member 562as one example of a fixing portion for removably fixing the filterfixing member 562 to the exhaust duct 560. The claw portions 573 arearranged opposite to each other. Engagement portions 574 with which theclaw portions 573 are engaged are formed in the outer peripheral surfaceof the other end 570 of the exhaust duct 560.

Inwardly projecting claws 575 are formed in the claw portions 573. Theengagement portions 574 are step-shaped so that the claws 575 of theclaw portions 573 may be engaged therewith. The claws 575 are engagedwith the engagement portions 574 such that the lower wall 572 of thefilter fixing member 562 is liquid-tightly fixed to the peripheral edgeof the duct opening 571 with the seal member 562 a interposed inbetween. Thus, the duct opening 571 is covered with the filter 561.

In addition, as indicated by an arrow in FIG. 15, the claw portions 573deform to open outward when urged outward. The claws 575 and theengagement portions 574 are disengaged if the claw portions 573 deformto open outward, so that the filter 561 can be attached/detached.

Next, the fixing structure of the fan cover 552 and the cover member 52is specifically described. As shown in FIG. 14, the flange 557 of thefan cover 552 is in contact with the upper surface of the cover member52. A metal fan cover plate lower 580 is disposed on the lower surfaceof the cover member 52. The fan cover plate lower 580 is frame-shaped,and has a peripheral edge 581 facing the flange 557 of the fan cover 552through the cover member 52.

The fan cover plate lower 580 is fixed to the cover member 52 by rivets582, and a plurality of upwardly projecting weld bolts 583 are weldedand fixed to the fan cover plate lower 580. FIG. 17 is a sectional viewthrough the weld bolt 583 provided at the rear end of the fan coverplate lower 580. Incidentally, the battery module 60 is not shown. Asshown in FIGS. 14 and 17, bolt insertion holes 584, 585 for theinsertion of the weld bolt 583 are formed in the part of the flange 557of the fan cover 552 and the part of the cover member 52 that face theweld bolt 583.

Furthermore, a metal fan cover plate upper 586 is provided in the rangeof the upper surface of the flange 557 of the fan cover 552 where thebolt insertion hole 585 is formed. The fan cover plate upper 586 isshaped to be divided into parts, and includes, in the presentembodiment, first to third fan cover plate uppers 587, 588, 589.

The first fan cover plate upper 587 is disposed at the left end. Thesecond fan cover plate upper 588 is disposed at the right end. The thirdfan cover plate upper 589 is disposed at the rear end. The first tothird fan cover plate uppers 587 to 589 are formed in accordance withthe shapes of the parts of the flange 557 in which these fan cover plateuppers are arranged. Bolt insertion holes 590 for the insertion of theweld bolts 583 are formed in the first to third fan cover plate uppers587 to 589.

As shown in FIGS. 14 and 17, collars 591 are received in the boltinsertion holes 584, 585 formed in the flange 557 of the fan cover 552and the cover member 52. The weld bolt 583 is inserted through the boltinsertion holes 584, 585, 590 and through the collar 591, and thenscrewed to a nut 592.

Seal members 593 are provided between the nuts 592 and the first tothird fan cover plate uppers 587 to 589, between screw holes of the nuts592 and the weld bolts 583 and between the fan cover 552 and the covermember 52. Clearances in between are liquid-tightly sealed. Thus, thereis no entry of a liquid such as water into the fan cover 552 from theoutside.

The rivets 582 are located further inside the cover member 52 than theabove-mentioned seal member 593. The entry of a liquid from the outsideis prevented by the seal member 593 in the space inside the seal member593 in the cover member 52. Therefore, after the rivet 582 is fixed tothe cover member 52 with a washer 582 a interposed in between, there isno need to provide a seal member around the insertion hole of the covermember 52 through which the rivet 582 is inserted. In addition, therivets 582 are welded to the fan cover plate lower 580, so that the fancover plate lower 580 is inhibited from dropping into the battery case50 while being fastened to the nut 592.

FIG. 18 shows the fixing structure of the cover member 52 and the fancover 552 in a part different from the part shown in FIG. 17. As shownin FIGS. 17 and 18, a peripheral edge 594 of the fan cover plate lower580 and a peripheral edge 595 of the fan cover plate upper 586 do notoverlap each other in the vertical direction (fastening direction of thebolt 583 and the nut 592).

The fan cover 552 is fastened to the cover member 52 by the weld bolt583 and the nut 592. On the other hand, the fan cover 552 and the covermember 52 are interposed between the fan cover plate upper 586 and thefan cover plate lower 580, thereby increasing the likelihood ofmaintaining the liquid-tight state upon the occurrence of damage to theresin fan cover 552 and cover member 52 caused by the force of fasteningthe weld bolt 583 and the nut 592.

The force of fastening the weld bolt 583 and the nut 592 is received bythe cover member 52 and the fan cover 552 from the peripheral edge 595of the fan cover plate upper 586 and the peripheral edge 594 of the fancover plate lower 580. However, the peripheral edges 594, 595 of the fancover plate lower 580 and the fan cover plate upper 586 do not overlapeach other in the vertical direction (fastening direction of the bolt5835 and the nut 592), so that the load input by the fastening force isnot concentrated at points in the cover member 52 and the fan cover 552.

In addition, as shown in FIG. 18, the width L1 of the fan cover plateupper 586 (the first to third fan cover plate uppers 587 to 589) may besmaller than the width L2 of the fan cover plate lower 580.Alternatively, the width L2 may be smaller than the width L1. Thus, theperipheral edges 594, 595 do not overlap each other in the verticaldirection (fastening direction of the bolt 583 and the nut 592). Inaddition, the relation of the arrangement of the peripheral edges 594,595 and the relation between the width L1 and the width L2 are similarin parts other than the parts shown in FIGS. 17 and 18.

Next, the fixing structure of the cover member 52 and the exhaust fan551 is specifically described. As shown in FIG. 14, exhaust fan fixingportions 600 are formed at three places in the peripheral edge of thelower end of the exhaust fan 551. FIG. 19 is a sectional view of thevicinity of the exhaust fan 551. FIG. 19 shows the vicinity of theexhaust fan fixing portion 600. In addition, the structures of theexhaust fans at the other two places may be similar.

As shown in FIG. 19, the exhaust fan fixing portion 600 includes an arm602 circumferentially extending from a housing 601 of the exhaust fan551, and a cylindrical absorber 603 provided at the end of the arm 602.

As shown in FIG. 14, upwardly projecting weld bolts 604 are provided inthe parts of the fan cover plate lower 580 located under the exhaust fan551 (absorber 603). The weld bolts 604 are fixed to the fan cover platelower 580 by welding. In addition, the fan cover plate lower 580 is inthe shape of a frame having the peripheral edge 581 as described above,and a plurality of beams 611 are also formed in the peripheral edge 581so that a plate part is also located under the absorber 603.

Bolt insertion holes 605 through which the weld bolts 604 can beinserted are formed in the part of the cover member 52 facing the weldbolt 604. As shown in FIG. 19, the absorber 603 is an elastic body, andallows the weld bolt 604 to be inserted therethrough. A collar 606 isinserted in the bolt insertion hole 605 formed in the cover member 52.Further, a cylindrical spacer 607 which allows the weld bolt 604 to beinserted therethrough is interposed between the cover member 52 and theabsorber 603. A washer 608 is provided on the upper surface of theabsorber 603 in an interposed manner.

The weld bolt 604 passes through the bolt insertion hole 605 and throughthe collar 606, the spacer 607, the absorber 603 and the washer 608, andthen screwed to a nut 609. The exhaust fan 551 is fixed to the covermember 52 by the weld bolts 604 and the nuts 609.

A space is defined between the exhaust fan 551 and the cover member 52by the spacer 607. Moreover, the absorber 603 is provided to absorb thevibration of the exhaust fan 551. Owing to the above-mentioned space andthe absorber 603, the vibration of the exhaust fan 551 is not easilytransmitted to the cover member 52.

A circumferentially outwardly extending flange 610 having a circularplanar shape is formed on the peripheral edge of the lower part of thespacer 607. The flange 610 is in contact with the upper surface of thecover member 52. The width L1 of the fan cover plate lower 580 is largerthan the width (diameter) L3 of the flange 610. In other words, theflange 610 is received within the plate portion of the fan cover platelower 580. Further, a peripheral edge 613 of the flange 610 of thespacer 607 does not overlap the peripheral edge 594 of the fan coverplate lower 580 in the vertical direction (fastening direction of thebolt 604 and the nut 609).

Thus, a load input from the peripheral edge 613 of the flange 610 of thespacer 607 acts on a part of the cover member 52 different from a parton which a load input from the peripheral edge 594 of the fan coverplate lower 580 acts. As a result, these loads are not concentrated, andthe strain within the cover member 52 due to the fastening force by thebolts 604 and the nuts 609 is reduced. Moreover, the vibration of theexhaust fan 551 on the cover member 52 is inhibited from beingconcentrated.

FIG. 20 is a sectional side view schematically showing the position ofthe rear portion of the battery unit 14 and the position of the motor12. As described above, the battery unit 14 is located ahead of themotor 12. The motor 12 is fixed to a cross member 900 via a bracket 612.

The cross member 900 is located behind the battery unit 14 attached tothe vehicle body 11, and located ahead of the motor 12. The cross member900 is formed, for example, across the side members 31, 32, and formspart of the frame body structure 30. In addition, the motor 12 is notexclusively fixed to the cross member 900 via the bracket 612. Thefixing structure of the motor 12 is not limited.

The battery unit 14 includes, as a reinforcing structure, the batteryprotector 620 and the third fan cover plate upper 589. FIG. 5 shows thebattery protector 620 removed from the battery case 50. As shown in FIG.5, the battery protector 620 is fixed to the rear end of the batterycase 50.

The battery protector 620 has a forwardly open concave shape. Thebattery protector 620 has a rear wall 621 disposed on the rear end ofthe flange 95 of the cover member 52, and a pair of side walls 622disposed on the right and left ends of the flange 95. The rear wall 621and the pair of side walls 622 are formed integrally with each other. Aprotector flange 623 overlapping the flange 95 is formed on the loweredges of the rear wall 621 and the pair of side walls 622.

The battery protector 620 is formed of a metal plate member. Theprotector flange 623 is fixed to the battery case 50 by the bolts 96 andthe nuts 97 that fix the tray member 51 and the cover member 52together. Specifically, the lower end of the battery protector 620 isfixed to the tray member 51 by the bolts 96 and the nuts 97. The traymember 51 is sufficiently rigid as to mount the plurality of batterymodules 60 thereon, and the battery protector 620 is therefore firmlyfixed.

As shown in FIG. 20, the rear wall 621 is inclined forward up in thevertical direction. Moreover, the rear wall 621 is wave-shaped in thevertical direction to improve its rigidity. The upper end of the rearwall 621 extends to the vicinity of the upper end of the cover member52. The third fan cover plate upper 589 is substantially L-shaped.

The rear wall 621 of the battery protector 620 is inclined forward.Thus, when the rear end of the electric vehicle 10 is subjected toimpact due to, for example, collision, the cross member 900 is guided bythe rear wall 621 and thereby moved obliquely upward and forward even ifthe motor 12 and the cross member 900 are moved forward by thecollision, as indicated by a two-dot chain line in FIG. 20. Therefore,even if the cross member 900 and the motor 12 are moved forward due tothe input of a load from behind, the collision between the cross member900 and the battery case 50 can be reduced.

Furthermore, the third fan cover plate upper 589 is L-shaped, so thatthe rigidity of the rear end of the cover member 52 improves. Thisinhibits the deformation of the rear end of the battery case 50 andtherefore inhibits the impact on the battery modules 60 stored in thebattery case 50. Thus, possible firing of the battery modules 60 isinhibited.

Moreover, the number of components is reduced by the use of the thirdfan cover plate upper 589.

Next, the flow of the cooling air inside the battery case 50 isdescribed.

As shown in FIG. 1, when the battery modules 60 are charged, the exhaustfan 551 and the heat exchanger unit 15 are driven so that the coolingair discharged from the heat exchanger unit 15 is guided to the coolingair inlet 86 through the cooling air duct 522.

As shown in FIG. 11, part of the cooling air let in from the cooling airinlet 86 is guided to the bypass exit opening 534 by the forefront rib523. In this case, as shown in FIG. 10, the cooling air can pass throughthe cuts 520 formed in the corners 519 of the battery modules 60, sothat the flow of the cooling air in the vicinity of the forefrontbattery module 60 is not blocked. The cooling air which has entered thebypass duct cover 531 from the bypass exit opening 534 bypasses thefront battery storage 55 and reaches the bypass entrance opening 535.

The remaining cooling air which does not enter the bypass exit opening534 passes through the front battery storage 55. At the same time, thecooling air is guided downward by the ribs 523 as indicated by an arrowin FIG. 11. The cooling air flowing downward is guided to the backwardlydownwardly inclined front longitudinal partition 503, and flows rearwardthrough a space defined between the bottom wall 505 and the batterycells 512.

At the rear end of the front battery storage 55, the cooling air flowingin from the bypass entrance opening 535 (the cooling air which hasbypassed the front battery storage 55) joins the cooling air which hascooled off the battery modules 60 in the front battery storage 55. Thejoined cooling air passes through the tunnel 532 and the first andsecond flow paths 533 a, 533 b and cools off the battery modules 60 inthe central battery storages 57, and then enters the rear batterystorage 56.

In the rear battery storage 56, the cooling air equally flows toward thefirst and second outlets 555, 556. The cooling air which has entered thefan cover 552 through the first and second outlets 555, 556 isdischarged to the front lower side of the vehicle body 11 through thefan exhaust opening 558, the fan cover outlet 559, the filter 561 andthe duct opening 571.

In the battery unit having such a configuration, the front and rearlongitudinal partitions 503, 509 are inclined forward and rearward, sothat the rigidity of the battery case 50 is assured, and at the sametime, the range of the battery module 60 covered with the front and rearlongitudinal partitions 503, 509 can be reduced.

Consequently, the area of contact between the cooling air and thebattery modules 60 can be increased, and the battery modules 60 can thusbe efficiently cooled off.

Moreover, the front longitudinal partition 503 is inclined to becomelower backwardly, and the rear longitudinal partition 509 is inclined tobecome higher backwardly.

Consequently, the cooling air smoothly flows from the cooling air inlet86 to the first and second outlets 555, 556, and the battery modules 60are thus efficiently cooled off.

It goes without saying that in carrying out the present invention,appropriate modifications can be made to the components of the electricvehicle of the present invention, including the frame body structure,the battery unit and the beam members.

According to the present invention, it is possible to provide a batteryunit capable of maintaining sufficient rigidity of a battery case andalso efficient cooling of a battery.

What is claimed is:
 1. A battery unit comprising: a battery case havingan inlet to let in a cooling gas and an outlet to let out the gas; and aplurality of battery modules stored and held in the battery case,wherein the battery case includes, a front battery storage, formed in afront side of the battery case, which contains an inlet side batterymodule group comprising a part of the plurality of the battery modules,a rear battery storage, formed in a rear side of the battery case, whichcontains an outlet side battery module group comprising a part of theplurality of the battery modules, and a central battery storage and anelectric circuit storage formed between the front battery storage andthe rear battery storage, the battery case having a passage extendingbetween the front battery storage and the rear battery storage to allowthe cooling gas to flow from the front battery storage to the rearbattery storage, and the passage extending at a position not in contactwith the electric circuit storage to prevent the cooling gas fromflowing into the electric circuit storage, wherein the battery caseincludes, a tray member on which the battery modules are disposed, acover member which covers the tray member, and the cover member has aconcaved position, at a position opposing the electric circuit storage,concaved to a lower direction of a vehicle than at positions opposingthe front battery storage and the rear battery storage, and wherein thecover member includes a tunnel, and the tunnel is arranged in a positionopposing the electric circuit storage, and a section thereof rises in anupper direction.
 2. The battery unit according to claim 1, wherein, theconcaved position opposes a recess of a floor panel of a vehiclearranged above the battery case.
 3. The battery unit according to claim1, wherein, a two-way flow passageway for cooling air which diverges inboth of a width direction of the vehicle is disposed in a rear directionof the vehicle of the tunnel formed in the cover member.